Improvement of Thermal Stability in Dual Mechanism Memory Using Hf_xAl_1-xO Blocking Layer for 3D V-NAND Flash Application

Dual mechanism memory, which combines charge trapping and polarization switching, was demonstrated as a way to overcome the limited memory window of charge trap flash (CTF) memory. However, due to the poor thermal stability of the Hfy Zr<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {1-y}}$ </tex-math></inline-formula>O (HZO) film, the dual mechanism memory scheme cannot be integrated into the current 3D V-NAND flash device fabrication process where the poly-silicon channel is deposited and annealed after the HZO blocking layer is deposited. In this study, HfxAl<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {1-x}}$ </tex-math></inline-formula> O (HAO) is investigated as the blocking layer due to its superior thermal stability. The dual mechanism memory with HAO blocking layer has achieved a 47% larger memory window compared to the device with HZO blocking layer. It is also demonstrated that the expanded memory window of the dual mechanism memory with HAO enables quad-level cell operation (QLC) with 1 V spacing between each state.